Thank you for the reply.
Sorry about the image, I have uploaded it to 2 places now, hope one of them works.
I already own a trenchcoat that goes as an overcoat, and it's large enough to fit over a jacket. That's not the purpose of this trenchcoat, it's meant as a 'trendy' coat over shirts and/or light knitwear on days that aren't so cold. This also means that the top button doesn't really need to be fastened.
It is supposed to be slim-fitted. Everything feels like a very good fit on me but my worry is the chest area...
On the picture I am wearing 3 layers under the coat; a t-shirt, a l/s shirt and a chunky knit cardigan (pretty packed) and am slightly pulling back my left shoulder to emphasize the 'problem' area.
It's a Burberry Prorsum trench and the biggest size in store was a 54 and only the chest goes up an inch and waist goes up half an inch. Shoulders, sleeve and total length stay the same. I am guessing this indicates it is not a traditional 'overcoat' trenchcoat.
I am still able to return the coat untill upcoming tuesday, so I have a little time to think it over. Ofcourse I consulted a few people like friends and family and they all think it's a nice coat and it fits, but they aren't really into clothing like some people on this board might be.